1. Field of the Invention
The present invention relates to the management of computer networks and in particular to the communications which are sent via the network to achieve such management.
2. The Prior Art
It is well known to enable computing devices to communicate with each other by connecting them together in networks, for instance local area networks (LANs), which operate according to predetermined communication protocols and enable data to be shared by the various computing devices. To facilitate the interconnection of computing devices it is known also to provide communication devices which each have a plurality of ports to each of which ports can be connected a computing device or another communication device. By building up a network of communication devices a large number of computing devices can be interconnected in a single network and thereby enabled to communicate with each other.
As networks have grown larger, and the communication devices have grown more sophisticated, it is also known to provide management of the network. To enable a management to achieve the desired purpose it is necessary for it to be provided the details of how the network is functioning and for this purpose communication agents have been developed which, in addition to providing their basic communication function for the computing devices in the network, also collect information relating to the operation of the network. A "central" management agent can then communicate with management devices within the communication agents themselves, recover the collected information and, on the basis of the recovered information, perform the necessary management functions.
During normal operation of the network, the management devices collect the information mentioned above relating to the operation of the network and builds up values in a Management Information Base (MIB). Data relating to a number of different parameters may be collected in the MIB and different data within the MIB are commonly referred to as "objects", each having its own object identifier (OID). As the data builds up, a number of different values may be stored in relation to each OID, perhaps 10s 100s or 1000s of values, which different values are retained in the MIB in an indexed form so any required value may be accessed.
There has been proposed a particular protocol according to which communications which are concerned with the management of the network are to meet. This is known as the Simple Network Management Protocol (SNMP) and in a basic implementation of this protocol, the management agent sends a communication to a particular communication device which identifies the information required and in response the communication device sends a reply providing the requested information. In particular, each communication within the SNMP protocol comprises two parts, one of which contains the OID and the other contains the value. IN SNMP communications sent by the central management agent, the value may identify which indexed value in the identified object it is desired to access. Alternatively, as the management agent may not know how many value are within the object in question, the value field may indicate a "GET NEXT" request which is asking for the next value in the object from that which was accessed previously. In reply SNMP communications the value field carries in returned value from the MIB.
In its most basic form, an individual SNMP request and reply must be sent for each value in the MIB it is desired to read, and so a large sequence must be sent if for instance it is desired to read all or a number of the indexed values associated with a particular object. Additionally it is likely the case that the number of bits used to send the OID and other controls is larger than the number of bits used to represent the returned value itself. In this most basic form then, SNMP can cause a very large increase in the amount of traffic on the network, at times sufficient to cause a deterioration in the performance of the network in its principal function of allowing the computing devices to communicate with each other.
This significant increase of traffic results from the fact that each SNMP communication which is sent according to the basic system outlined above, must include the identification of the object information which it is desired to access and, as mentioned, this identifier is typically quite long and therefore takes up a significant proportion of the SNMP communication which is sent, and the response which is returned.
The need for the management device to send a separate communication for each item of information required also causes significant delays in the obtaining of the information required by the management device.
One scheme which has been previously proposed to reduce these problems has been to define a single object within the protocol, which is called an "accelerator object". The accelerator object has its own OID which is used to send and reply to requests within the SNMP protocol, but it is defined within the management devices as relating to a number of different objects and/or values within the MIB. The requested values from the MIB are combined together and sent in the value field in the SNMP reply sent by the local management device.
This accelerator object system therefore provides for a more efficient transfer of data back to the central management agent. In particular a large number of values perhaps relating to different objects can be returned simply by issuing a single SNMP request and receiving a single reply.
The system is however relatively inflexible. Whereas, in the basic arrangement outlined above, the central management agent is able to request only the information it requires, although this may entail a large number of separate requests, with the accelerator object the information which is returned is predetermined. This may result in the management agent receiving and having to discard unwanted data, or having to send additional requests for data not defined within the accelerator object.